Why is this so? I can see heavy water and light water making a difference, but why should the pressure make such a difference to tritium production?

Most of the PWRs use boron to control the reactivity (while the BWRs don't use it). The boron is added in the primary coolant in the form of boric acid. This acidifies the water.

In order to get a a neutral pH they add LiOH to the primary water (LiOH rises the pH), so there are Li atoms in the water. The boron atoms also make 7Li when they capture a neutron. Some of the Li atoms (7Li and 6Li) absorb neutrons and make tritium.

There must be a fairly large amount of tritium on Earth already, naturally occurring or from weapons testing. Can't they just dump the tritiated water into the Ocean?

Virtually no tritium exists in the environment as a result of weapons testing.The last significant weapons test programme was in the 90s, which is 25 years or so ago now (the end of NTS use and the French in Polynesia).

That is several half lives, and the large scale nuclear testing in the 50s and 60s is a long time ago now.

Actually, the half life of tritium is 12.32 years, so only about 3/4 of the environmental tritium left after large scale testing stopped has decayed. The Canadians deal with a lot of tritium because they use heavy water as a moderator. So it is possible to deal with.

During manufacture, a length of borosilicate glass tube that has had the inside surface coated with a phosphor-containing material is filled with radioactive tritium. The tube is then sealed at the desired length using a carbon dioxide laser. Borosilicate is preferred for its strength and resistance to breakage.

I would prefer a refillable bottle instead of a welded bottle – or I guess so. Although the glowing bottle should be recyclable, refilling at home could not be allowed, because inhaling tritium is a health risk.

Quote:

Tritium is an isotope of hydrogen, which allows it to readily bind to hydroxyl radicals, forming tritiated water (HTO), and to carbon atoms. Since tritium is a low energy beta emitter, it is not dangerous externally (its beta particles are unable to penetrate the skin), but it can be a radiation hazard when inhaled, ingested via food or water, or absorbed through the skin.

I did read an article that had a graphic that showed all the sources of radioactivity in the Oceans and basically, man made sources were totally insignificant compared to those that were there already.

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